Dopamine is present in a special type of cell in the superior cervical ganglion. The cells are known as small intensely fluorescent cells (SIF cells) because of their appearance after histochemical staining for catecholamines. These cells probably modulate information transfer from preganglionic neurons to post-ganglionic neurons. Our present objectives are to evaluate the influence of the preganglionic neurons on the metabolism of dopamine in the rat superior cervical ganglion.